Method of processing wood pulp



Nov. 24, 1953 s 2,660,097

METHOD OF PROCESSING WOOD PULP Filed April 16, 1949 PULP PULP COOKINGGRINDING V GROUNDWOOD BYPASS REFINING r S EREENING SCREENING MIXING vPAPER MAKING IN VEN TOR. HAROLD 5'. HILL "W ATTORNEY it;

Patented Nov. 24, 1953 METHOD OF PROCESSING WOOD PULP. 7

Harold Sanford Hill, Kenogami, Quebec, Canada,

assignor to Price; Brothers & Company, Limited, Quebec, Canada, acorporation of Quebec,

Canada Application April 16, 1949, SerialNo. 87,893

, 1 a The present invention relates to the mechanical processing of pulpfor'papermaking. More particularly the invention relates to themechanical processing of chemical pulps, such as sulphite pulps, by thepulp treating method disclosedin the pending U. S. patent application ofthe present inventor and Joseph Edwards, Serial No. 565,128, filedNovember 25, 1944, which has now matured into Patent No. 2,516,384,granted July In the process of Patent No. 2,516,384, the pulp, which isto be treated, is brought to, a state in which its mass is made up ofsmall, discrete nodules moist with an aqueous liquid; a layer of thenodulated pulp is compressed between two working surfaces, which areroughened or figured to have good traction with the pulp withoutentangling the fibres; and the nodulated pulp is caused to rolltractively in traverse of and under compression by the-surfaces in suchway that the nodules are continuously or frequently reoriented withreference to the direction in which the nodulated pulp rolls in traverseof the surfaces. The reorientation of the nodules may-be effected invarious ways. A preferred method is by causing the direction in whichthe nodulated pulp rolls in traverse of the surfaces to changecontinuously with reference to the surfaces along curved paths. Apreferred Way of accomplishing this continuous change in direction ofroll of the nodulated pulp over the surfaces is to impart portantapplications of the process of the patent mentioned has been that oftreating high yield chemical pulp. One of thefundamental requirementsfor carrying out theprocess of Patent No.2,516,384 is that true rollingtraction of the pulp on the working surfaces be maintained at all times.The pulp must not slip on the surfaces; and slip or shear planes mustnot be allowed to develop.

within the pulp itself. If such slippage'occurs, or if shear planesdevelop Within the pulp, the rolling traverse of the pulp over theworking surfaces ceasesat once; the pulp forms into 4 Claims. (01. 9220) pulp so that it may readily, be processed I methodof Patent No.2,516,384. i

2 matted sliding layers; and the functioning of the process as suchcomes to a complete stop. 3

It has been found that slippage occurs and shear planes develop if therolling traverse of the pulp over the surfaces exceeds a criticalvelocity, andfurther, if the compression of the pulp during rollingexceeds a critical pressure. The two factors, velocity of rolling'andpressure, are to a considerable extent interdependent, the lower thevelocity, the high thepressure that can be employed without loss 'oftraction and vice versa. In practice, the speed of relative movement ofthe working surfaces is usually in the range of to 300 feet per minute,and the pressure exerted on the pulp by the surfaces is usually in therange of 5 to 20 pounds per square inch of opposed surfaces compressingthe pulp.

It will be apparent that the velocity of rolling and the appliedpressure combine to provide a measure of the power input, and thatsincethere are definite limits ,to both velocity and pressure incarrying outithe process, it follows, in turn,

that there is a definite limit to the intensity of power input that may.be used. This is a factor of great importance in, the practicalapplication of the process of Patent No. 2,516,384 since it imposesalimit on the work that can be obtained from a given area ofworkingsurfaces; in short, it puts a limit on the capacity of a givenprocessing machine. V r Y As far as is known, this ability of a pulp toabsorb power in rolling under compression is one that, prior to theinvention of the process of Patent No. 2,516,384, had received norecognition or interest. Indeed, it is a property of pulp which as yethas been given no name in the art. For the purpose of the presentapplication this property is designated as traction. A pulp,,which hasmarked ability to absorb power when treated by the process of Patent No.2,516,384, is said to possess high traction; a pulp, which has poorability toabsorb power when treated by such process, is said to possesslow traction. Various kinds and grades of chemical pulps exhibitdifferent amounts of traction. High-yield sulphite pulps have relativelylowtraction, and, in gen eral, the traction becomes less and lesswith:in-

creasing: yield. a

a A primary object of the present invention is to improve the tractionof chemical papermaking by the Another object of the, invention is toimprove the efficiency .of the method 'of Patent No. 2,516,384 thetreatment of chemical pulp,

Still another object of the invention is to provide an improved methodof preparing a lowcost furnish in the manufacture of newsprint paper. pp Othenqbjectspj the invention; wilhbeapparent b tl en nmz the, spec atin and r m the recital of the appended claims.

I have found that the traction of a chemical pulp may be raised to anotable degree by iiicorporating with the chemicalip'ulp sb'rrid'giohfidwood. By groundwood is m ,thewe llknown 'pu p made. byhp s n Qwaiiilstzthe atef f arevolving grindstohe. v W In the method of thepresent application a minorfraction of 'groundwood is added to thechemical pulp prior to meclranieal -proeessing- An example will serve toillustrate the rema1 -k-- able improvement in operating eflicienc'y thatmeme achieved t: thism tho. lan nsta lanon 19; car ying, out the1p''pssfgf PatefifiNo. v. ;38?

'lr oun wood -may be added m thBcHniiul rza v v r l o ipr qr'i es ngthe; chemicalfpulpfby the metho e No x516 3845 and in 1 convenientIiFcentinuous process it is'of course-preferable that -the i groundwoodbe added at a uniform, controlledrates The amount -"o-f groundwdo'd,which is used, may vary over a con'siderab'le range depending-on=- gthe:operating requirements in:aapartieular'caseh In someinstances 3% of 25%.lorzevemhigherlomgroundwooclsadditicn may be reeuiredsa I have foundfurther that the method of the 75 7 main:

grinders; andz their; screened. The mixture, in-

eluding any desired coloring matter, is then passejditotheafie'qfmachine. The proportion of sulphite p11 :m' the furnish isusually in the In some cases, a portion of mineral wading material isadded before or ati'i theipapeniirachine.

In the accompanying drawing: Fig; lis a flow sheet,illustratingdiagrammatic a 1l y one way in which an improved, low costfiewsp'rir'it' furnishniay beprepared by: themetho'dEoft-he'presentinvention.

I my never system: of preparing newsprint m the? groundwate maybe'made'in the usu l=w'a'y; butfthe s'ulphite pulp maybeimadet61iaV=a'-higHr-- ie'lii ofi thei basis of tlie wood used in theran'ge'of 5 55 to '7 5 theincreased yieldfleeing--obtainedhy the use o'f milderco'oling conditionsat I the digester, is: well known in the art. Thegroundwood passes, of course;v from the' pulp grinding station to thesereeniri'g statiori -w-here the usual screening operations" are carried01 115 426) eliminateoversize-material.

With theiiiethbd of the present invehtion; a small pertion ofthe'screened groundwoodl usually mane range or mew to 8% -of-thetotafiamount of groundwo'od-t is hy pass'd and mined with the unrefined'hig li yil d sulphitepulpcdrhihgfifdm the} digester;the-proportionbein'g usually: in the range o'f to 40 -gi'oiindwooditoewam soyz,

of? hi'g'h y'ield str'lphites' The mixturef o'fthe two-madefupfofsmall;moist} discrete nodirlfw usually v ..r or translatory'motiorr about" an axis extending iii-"the direction of appl-iedpfessure-- the compressed nodulated pulp is rolled over the Working"surfaces-"in" continuously changing directiens and. the individualfibers reaherehy fcharaeteg lparticularly suitdttd ithejrepiu'irefnentsot e s rm manu e and qua i- Pe -i V thegpresence of zthe groundwood,,the :refinerrcan operate at high capacity and efficiency."

. v The:processed;;mixedrpiilpyfrom theerefiner is thempn-tgth-rouehzzthe' usualqscreening goperation, illustrated: in zFiei-a.1.-.-. A. p lpfw h nez p may beqincluded-rif desiredtg. The screened.mi-xtureris {then mixedlineregulated:amount iwithnthe untreated;greundwood :represents usual1y =,-9;2%- to99;5%" oftthe .total; amountof gmundwoodmsed. Tha-combined pul-ps; namely, the :mixture ofvuntreatedgroundwood and-of; the refined-vmi ti rlei f c mical ii ianee oundwconstitutes the furnish, and are then delivered to the papermakingmachine for treatment in the usual way.

Fig. 1 shows diagrammatically the above described steps in thepreparation of the newsprint furnish as appiled in an integrated pulpand newsprint manufacturing operation.

While the invention has particular application to the processing of pulpby the method of Patent No. 2,516,384, it may also be used withadvantage in other mechanical processes for refining pulp. While aparticular embodiment of the invention and a particular use thereforhave been described, then, it will be understood that the invention iscapable of further modification and use, and this application isintended to cover any variations, uses, or adaptations of the inventionfollowing, in general, the principles of the invention and ineludingsuch departures from the present disclosure as come within known orcustomary practice in the art to which the invention pertains and as maybe applied to the essential features hereinbefore set forth and as fallwithin the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

1. The method of preparing a papermaking furnish made up of to 25% rawchemical wood pulp as one component and of 90% to 75% of groundwood asanother component, which includes as one step the rolling of moist,nodulated pulp tractively in traverse of and under compresthereby toincrease the ability of the pulp to v absorb working power withoutslipping or smearing on the working surfaces, bringing the mixture to astate in which its mass is made up of small, moist, discrete nodules offibres at high consistency, compressing the nodulated mixture betweentwo opposed working surfaces which are roughened to provide traction forthe pulp without obstructing rolling traverse of the pulp nodules onsaid surfaces, rolling the nodulated mixture tractively in traverse ofthe working surfaces while it is under compression between them torefine the mixture, and then mixing the balance of the groundwoodcomponent of the furnish with the refined mixture.

' 2. The method of processing a slippery, moist chemical pulp whichcomprises increasing the ability of the pulp to absorb working powerwithout slipping by adding to the moist chemical pulp a minor proportionof groundwood prior to refining the pulp, and then refining the pulp byforming the mixture of pulp and groundwood into small, moist, discretenodules, comprises the 7 mixture while in a moist nodulated statebetween two opposed working surf aces which are roughened to providetraction for the pulp without obstructing, rolling traverse of the pulpnodules on the working surfaces, and rolling the nodulated mixturetractively in traverse of and under compression between the two opposedworking surfaces.

3. The method of utilizing a' slippery, raw, high-yield, chemical pulpin newsprint furnish which comprises adding to the slippery, raw pulp aminor proportion of groundwood, thereby to increase substantially theability of the pulp to absorb working power without slipping when theraw pulp is refined by causing it to roll in moist, nodule form undercompression between opposed working surfaces, forming the mixture of rawpulp and groundwood to a state of small, discrete, moist nodules,compressing the nodulated pulp between two opposed working surfaceswhich are roughened to have tractive contact with the pulp withoutobstructing rolling traverse of the pulp nodules on the surfaces,causing the compressed, nodulated mixture to roll under compressionbetween and across the two opposed working surfaces to refine it, andthen adding to the refined mixture an additional major proportion ofgroundwood to form newsprint furnish.

4. The method of producing a papermaking furnish from a high-yield, raw,chemical pulp, which comprises first mixing a minor proportion ofgroundwood with a moist, raw, high-yield chemical pulp, thereby toincrease the ability of the pulp to absorb working power withoutslipping or smearing when rolled between opposed working surfaces,forming the mixture into small, discrete, moist nodules, compressing thenodules between two opposed working surfaces which are roughened toprovide traction for the pulp without obstructing rolling traverse ofthe pulp nodules on the two working surfaces, and rolling the pulp onand across the two working surfaces while under compression to refinethe mixture, and then mixing additional groundwood with the refinedmixture to form the furnish, the percentage of chemical pulp in thefurnish being less than the percentage of the total amount of groundwoodemployed but being greater than the percentage of groundwood which ismixed with the chemical pulp before refining.

HAROLD SANFORD HILL.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date v 145,620 Brown et a1 Dec. 16, 1873 487,913 Carter et a1 Dec.13, 1892 657,206 Ferrell et al Sept. 4, 1900 693,941 Zilles Feb. 25,1902 1,372,640 Clapp Mar. 22, 1921 1,525,050 Savery Feb. 3, 19251,757,010 Fair May 6, 1930 1,881,419v Munroe Oct. 4, 1932 2,214,893 VonHassell Sept. 17, 1940 2,456,249 Bidwell Dec. 14, 1948 2,503,454 QuinnApr. 11, 1950 2,516,384 Hill et al. July 25, 1950 2,573,709 Hill et al.Nov. 6, 1951- 2,580,161 Driessen Dec. 25, 1951 OTHER REFERENCES ModernPulp and Paper Making Witham, 1942, 2nd ed., Reinhold Publishing Corp.,page 72.

Deinking of Paper by West, pagelO, (1943),

published by Institute of Paper Chemistry,

